Russian Foreign Minister Sergei Lavrov accused Ukraine on Monday of violating an accord reached in Geneva last week aimed at averting a wider conflict between the two neighbours.

"Steps are being taken - above all by those who seized power in Kiev - not only that do not fulfil, but that crudely violate the Geneva agreement," he said.

Lavrov also told a news conference that a deadly gunfight early on Sunday near the Ukrainian city of Slaviansk, which is controlled by pro-Russian separatists, was a crime and showed Kiev did not want to control "extremists".

"The authorities are doing nothing, not even lifting a finger, to address the causes behind this deep internal crisis in Ukraine," he said.

At least three people were killed in the shootout, shaking an already fragile accord reached last Thursday between Russia, Ukraine, the United States and the European Union.

The agreement called for an immediate end to violence in Ukraine, where Western powers believe Russia is fomenting a pro-Russian separatist movement, an allegation Moscow denies.

The accord also called for illegal armed groups to go home in a process to be overseen by Europe's OSCE watchdog. However, separatists have shown little sign of quitting public buildings in largely Russian-speaking eastern Ukraine.

Lavrov said the Ukrainian authorities had failed to remove illegal protests from squares in Kiev, Ukraine's capital.

"This is absolutely unacceptable," he said.

The White House has demanded Russia use what Washington believes is has over the separatists - Moscow insists it has none - to force them to vacate the buildings.

It has also warned of stronger economic sanctions than those already imposed if Moscow fails to uphold the Geneva deal.

"Before giving us ultimatums, demanding that we fulfil demands within two or three days with the threat of sanctions, we would urgently call on our American partners to fully accept responsibility for those who they brought to power," Lavrov said.

He added that attempts to isolate Russia would fail because it was "a big, independent power that knows what it wants."